钴卟啉-四丁基溴化铵串联催化苯乙烯在氧气和二氧化碳中合成碳酸苯乙烯酯

CoTPP-TBAB catalyzed tandem transformation of styrene carbonate from styrene in the presence of O2 and CO2

通过仿生催化,将苯乙烯、氧气(O2)和二氧化碳(CO2)直接合成环状碳酸酯在现代化学中极具学术研究意义和工业应用价值。采用钴卟啉-四丁基溴化铵为双组分催化剂,以2-氧代环戊烷羧酸甲酯为助剂,在O2和CO2条件下,直接将苯乙烯转化为碳酸苯乙烯酯。系统考察了催化剂用量等因素对催化性能的影响。在最佳反应条件下,苯乙烯的转化率高达99%,环状碳酸酯的收率可达35%。利用在线紫外与在线红外探讨了该串联反应可能的机理。结果表明,钴中心与2-氧代环戊烷羧酸甲酯的环内氧原子配位后活化氧气形成过氧活性物种,进而形成高价钴-氧中间体,其通过传递氧原子给苯乙烯而生成环氧苯乙烷。而后,环氧苯乙烷在四丁基溴化铵的催化作用下开环,并通过CO2插入反应和分子内闭环反应最终生成环状碳酸酯。

The direct synthesis cyclic carbonate from styrene,O2 and CO2 is of great academic attraction and industrial value in modern chemistry.The metalloporphyrin/tetrabutylammonium bromide was employed as binary catalyst for this reaction in the presence of O2 and CO2 by using methyl 2-cyclopentanone-carboxylate as cocatalysts.The effects of reaction parameters on catalytic performance were investigated systematically.Under the optimal reaction conditions,conversion of styrene(99%)and selectivity to cyclic carbonate(35%)were obtained.The possible mechanism of cascade reaction was proposed by using in-situ ultraviolet and infrared spectroscopy.The results show that the cobalt center is coordinated with the ring oxygen atom of methyl 2-oxocyclopentanecarboxylate to activate oxygen to form a peroxy active species,thereby forming a high-valent cobalt-oxygen intermediate,which passes oxygen atoms to styrene and generate epoxy styrene.Then,styrene oxide opened ring under the catalysis of tetrabutylammonium bromide,and finally formed cyclic carbonate through CO2 insertion reaction and intramolecular ring-closing reaction.